Is it possible to edit a file under different settings at the same time? More precisely, I'd like to have multiple buffers in the same instance of Vim which have the same content (changing one buffer affects the other buffer's content immediately), but different cursor positions, different marks, different syntax highlighting, etc.
Common use cases include editing different parts of the same file independently (without e.g. entering visual mode in one instance break the current visual mode selection in the other instance), and editing mixed-format files (e.g. HTML and Javascript) without having to switch settings. (An alternate approach for the second use case would be to change settings automatically based on the cursor position but that's out of scope for this question.)
An editor whose mention admittedly could shock calls this “indirect buffers”.